PHOTOINITIATED AND THERMOINITIATED CURING OF EPOXY-RESINS BY SULFONIUM SALTS

A number of benzylthiolanium salts have been synthesized, analysed and evaluated by differential scanning calorimetry and viscosity measurem ents with respect to their potential use as thermal curing agents for epoxy resins. Over a wide range of Hammett constants a correlation exi sts between initial reactivity, shelf life and the electronic substitu ent effects of the benzyl group. A combination with arylsulfonium salt s leads in singular cases to dual cure systems with attractive propert ies of thermal and UV induced curing. The sensitization of benzylthiol anium salts also leads to dual cure systems. This opens up new possibi lities for UV curable epoxy resins in electronic applications requirin g additional curing in shaded areas.